President Trump will press NATO allies to fulfill critical defense spending commitments at a summit in Turkey this week.
The push follows promises secured from member nations last year.
NATO's chief has requested that allies submit robust plans to reach spending benchmarks.
U.S. officials have portrayed intensifying tensions as "growing pains."
Observers show allies will obtain "report cards" to track their progress.
Various experts have cautioned of economic consequences if the demands are applied fully.